Polyolefins stabilized with a nickel glyoxime



United States Patent 3,261,790 POLYOLEFINS STABILIZED WITH A NIQKEL GLYOXIME Arthur C. Hacker, Forest Hills, and Otto S. Kauder,

Jamaica, N.Y., assignors to Argus Chemical Corporation, Brooklyn, N.Y., a corporation of New York No Drawing. Filed Nov. 23, 1962, Ser. No. 239,827 14 (Ilaiins. (Cl. 260-23) This invention relates to stabilizers comprising a nickel glyoxime capable of improving the resistance of propylene polymers and other olefin polymers to deterioration 'in properties when exposed to light, to propylene polymer compositions and to aprocess of stabilizing propylene polymers employing such stabilizers.

Polypropylene is a tough, high-melting polymeric material, but in several respects its stability leaves much to be desired. The polymer shows a tendency to decrease rapidly in melt viscosity, and then to become brittle, when kept at elevated temperatures for the time required in milling, calendering, extrusion, injection molding and fiber-forming equipment. This deterioration is particularly serious when the polymer is worked in the molten state in the presence of oxygen, e.g., air. Polypropylene is also subject to deterioration in physical properties when exposed to light, particularly to ultraviolet light or sunlight, over long periods of time. Shaped polymers show a tendency to discolor, to become distorted, to crack, and to powder around the edges upon exposure to sunlight and during aging, and especially when heated at moderately elevated temperatures as in an accelerated aging process, and again, the problem is accentuated in the presence of oxygen.

It has been proposed heretofore to employ nickel compounds to improve the resistance of polypropylene to such deterioration. Compounds such as nickel acctyl acetonate, nickel complexes of azo dyes, nickel complexes of salicylic aldehyde imines, and nickel complexes of phenols and phenol sulfides have been used. However, these compounds are unstable at elevated temperatures, and may decompose before the polymer, and before they can be eifective as stabilizers. Also, they have not shown as high a stabilizing action as the phenols and phenol sulfides, which have accordingly been preferred.

In accordance with the instant invention, a stabilizer is provided comprising a nickel glyoxime which improves the resistance to light-induced deterioration of olefin polymers, such as propylene polymers, and in combination with other olefin polymer heat and/ or light stabilizers, improves resistance to light and to both heat and light induced deteriorations, for long periods of time, as evidenced by observation of melt index. A preferred combination in accordance with the invention comprises a nickel glyoxime and a Z-hydroxy benzophenone. Such combinations display a more etfective stabilizing action against light-induced deterioration than either alone, suggesting that each component synergizes the stabilizing action of the other.

Purity of propylene polymers, extent of degradation, and resistance to embrittlement over long periods of time are characteristics capable of evaluation by observation of the change in melt index of the particular polymer. There is a direct correlation between the rate of increase in melt index and the rate of deterioration in the abovementioned physical propertie of the polymer. Nickel glyoximes significantly reduce the rate of increase in melt index under exposure to light, and also improve retention of color and other important physical properties of the polymer.

3 ,261,799 Patented July 19, 1966 The nickel glyoximes in accordance with the invention can be defined by the following formula:

In this formula, Z is a glyoxime radical attached to the nickel through an oxygen atom:

The Z radical can form a chelted heterocyclic ring including the nickel in the ring, by chelation with the glyoxime hydroxyl group:

In the above formulae, R R R and R represent hydrogen or monovalent organic aliphatic, aromatic and non-aromatic ialicyclic hydrocarbon or heterocyclic radicals having from one to about thirty carbon atoms. R and R and R and R can be taken together as bivalent organic aliphatic, aromatic or nonarom-atic alicyclic hydrocarbon or heterocyclic radicals having from three to about thirty carbon atoms.

As typical R radicals there can be mentioned methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isoamyl, hexyl, octyl, isooctyl, 2-ethyl hexyl, nonyl, octa decyl, behenyl, palmityl, lauryl, oleyl, linoleyl, ricinoleyl, phenyl, naphthyl, benzyl, a-phenethyl, ,B-phenethyl, xylyl, tolyl, cycloheptyl, cyclohexyl, cyclopentyl, and furyl, tetramethylene, trimethylene and 1,2-phenylene.

Exemplary glyoximes are nickel glyoxime, nickel methyl glyoxime, nickel dimethyl glyoxime, nickel methyl isopropyl glyoxime, nickel methyl hexadecyl glyoxime, nickel dinonyl glyoxime, nickel octyl canbomethyoxyheptyl glyoxime, nickel diphenyl glyoxime, nickel methyl phenyl glyoxime, nickel pentamet-hylene glyoxime, nickel decametihylene glyoxime, nickel tetramethylene glyoxime, nickel di-Z-furylglyoxime, nickel di-n tridec yl glyoxime, nickel phenyl 4-methoxyphenyl glyoxime, nickel d-i(2,4, 6- trimethyl phenyl) glyoxime, nickel di-l-naphthyl glyoxime, nickel di-(6-rnethyl-2-qui11olyl) glyoxime.

Nickel glyoximes are readily prepared by reaction of the corresponding diketone with excess hydroxylamine acetate to diorm the glyoxime, and then by double decomposition with a nickel salt of an inorganic or organic acid. These are known reactions, and form no part of the instant invention.

The invention also contemplates the formation of a nickel glyoxime in situ in the polyolefin composition or in the stabilizer composition by double decomposition of a glyoxime and a nickel salt of an organic acid such as an aliphatic, aromatic or cycloaliphatic acid having from two to thirty carbon atoms, such as lauric, acetic, stearic, ben zoic or cyclohexanoic acids. The acid is liberated in forming the nickel glyoxime, and if the acid is nonvolatile it will remain in the composition, so that a nonvolatile acid must be nondeleterious to be useful.

The nickel glyoximes of the invention are effective light stabilizers when used with olefin polymers, and especially propylene polymers, as the sole stabilizer. Their effectiveness is particularly evidenced by an improved resistance to an increase in melt index upon exposure to sunlight for long periods of time. They can also be used in conjunction with other propylene polymer light and heat stabilizers, wherein they are eifeetive in supplementing the stabilizing effects contributed bythe other stabilizers polychloroethyl,

without disadvantageously affecting the desirable properties of the polymer. In many cases, an enhanced or synergistic effect is observed.

As indicated, stabilizer compositions containing a nickel glyoxime and a 2-hydroxy benzophenone or derivative thereof are preferred for light stabilization. A benzophenone is effective that has a 2-hydroxyabenzophenone nucleus, i.e., a nucleus of the structure This nucleus is inclusive of the compound 2-hydIOXy b6Ib zophenone, and derivatives thereof bearing substituent groups attached to any of the ring carbon atoms of the nucleus.

The preferred benzophenones of this invention, containing a nucleus of the above structure, have the following general formula:

wherein the X-radicals are selected from the group consisting of hydrogen, hydroxyl, halogen (such as fluorine, chlorine, bromine and iodine, and preferably chlorine or bromine), nitro and R-radical of from one to about thirty carbon atoms; wherein the Y-radicals are selected from the group consisting of hydrogen, hydroxyl, halogen (such as fluorine, chlorine, bromine and iodine, and preferably chlorine or bromine), and R-radicals of from one to about thirty carbon atoms.

Within the above limitations, the X and Y radicals substituted on any ring or on different rings can be the same or different. That is, for instance, the para Y-radical can be an R-radical; while one ortho Y-radical can be the same or a different R-radical and the other ortho Y-raclical can be a halogen; and the two meta Y-radicals can be hydrogen. The X-radical on the other ring can be an R-radical, or a different radical; and if an R-radical they can be the same, or different, from any Y-radicals which are R-radicals. Other combinations will be apparent to those skilled in the art.

The R-radical is an organic radical and can be selected from the group consisting of aliphatic, alicyclic, and heterocyclic groups of from one to thirty carbon atoms. However, there is no upper limit, other than impracticability, on the number of R carbon atoms. Typical R- radicals are alkyl, alkenyl, alkynyl, cycloalkyl, acyl, aryl, alkaryl, aralkyl, al'koxy, aryloxy, 'alkaryloxy, aralkoxy, oxyalkylene, hydroxyalkyl, and hydroxyalkylene radicals, and esters thereof with organic carboxylic acids. These R-radicals may, if desired, contain inert, non-reactive substituents such as halogen and other carbocyclic and heterocyclic ring structures.

Typical R-radicals are, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, n-octyl, isooctyl, Z-ethylhexyl, t-octyl, decyl, ethylnonyl, ethylmethyloctyl, diethylheptyl, undecyl, dodecyl, pentadecyl, octadecyl, tricosyl, and nonacosyl; allyl, hexenyl, linoleyl, ricinoleyl, oleyl, uudecadienyl, propyloctadece-nyl, propynyl, methoxy, n-butoxy, n-octyloxy, 2-ethylhexyloxy, n-decyloxy, benzyloxy, acetoxy, benzoyloxy; hex ynyl, ethylheptadecadiynyl, undecynyl; monochloroethyl, monobromopropyl, polybromopropyl, fluoroheptyl, chlorododecyl, chlorododecenyl, chlorododecynyl, chlorotricosyl; hydroxychlorononyl, hydroxybromodecyl, hydroxybromotricosyl; hydroxyethyl, hydroxypropyl, monohydroxyundecyl, dihydroxyundecyl, hy-

droxyundecenyl, hydroxyundecynyl, glyceryl, sorbityl, pentaerythrityl, and polyoxyalkylene radicals such as those derived from diethylene glycol, triethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, and polyoxypropyleneoxyethylene glycol, and esters thereof with any of the organic aliphatic, alicyclic, or oxygencontaini-ng heterocyclic acids. By the term aliphatic acid is meant any open chain carboxylic acid substituted, if desired, with nonreactive groups, such as halogen, sulfur and hydroxyl. By the term alicyclic it will be understood that there is intended any cyclic acid in which the ring is nonaromatic and composed solely of carbon atoms, and such acids may if desired have inert, nonreactive substituents such as halogen, hydroxyl, alkyl radicals, alkenyl radicals and other carbocyclic ring structures condensed therewith. Exemplary of such acids are acetic, propionic, butyric, valeric, hexanoic, ethylheptanoic, n-octanoic, isooctanoic, capric, undeca-noic, lauric, myristic, palmitic, stearic, oleic, ricinoleic, behenic; chlorocaproic and hydroxycapric acids.

As typical examples of benzophenones that are intended to be included within the scope of this invention may be mentioned the following:

2-hydroxy benzophenone, 2-hydroXy-4-bromo-benzophenone, 2-hydroxy-4-methyl-benzophenone, 2-hydroxy-4-iodo4benzophenone, 2-hydroXy-4-pent achloro-benzophenone, 2-hydroxy-4abenzyloxy-benzophenone, 2-hydroXy-4,S-dimethyl-benzophenone, 2-hydroxy-4-benzyloxy-5 -chlorobenzophenone, 2-hydr0Xy-5 -heXyl-2,4-dimethyl-benzophenone, 2-hydroXy-4- 3,4-dichlorobenzyloxy) -4'-t-butylbenzophenone, 2-hyd roxy-3 -methyl-4'-nitrobenzophenone, 2-hydroxy- (4-hexyl) -benzophenone, 2-hydroXy-4-benzyloXy-2',4',5 '-trichlorobenzophenone, 2-hydroXy- (4-ethyl) -3 -chloro-benzophenone, 2, bdihydroxy-benzophenone, 2,2, 4-trihydroxybenzo phenone, and 4-n-decyloXy-2,2-dihydroxybenzophenone.

Additional heat stabilizers which can be used include, for instance, phenols, organic triphosphites, thiodipropionic esters, polyvalent metal salts of organic acids, organic mercaptans, and organic polysulfides.

When the nickel glyoxime is used in conjunction with a phenol the increased stabilizing effect is evidenced by improved resistance to yellowing, and an extended life, in terms of resistance to embrittlement and development of tackiness at elevated temperatures. The phenol stabilizers contain one or more phenolic hydroxyl groups, and can contain one or more phenolic nuclei. In addition, the phenolic nucleus can contain an oxy or thio ether group.

The alkyl-substituted phenols and polynuclear phenols, because of their molecular weight, have a higher boiling point, and therefore are preferred because of their lower volatility. There can be one or a plurality of alkyl groups of one or more carbon atoms. The alkyl group or groups including any alkylene groups between phenol nuclei preferably aggregate at least four carbon atoms. The longer the alkyl or alkylene chain, the better the compatibility with polypropylene, inasmuch as the phenolic compound then acquires more of an aliphatic hydrocarbon character, and therefore there is no upper limit on the number of alkyl carbon atoms. Usually, from the standpoint of availability, the compound will not have more than about eighteen carbon atoms in an alkyl, alicyclidene and alkylene group, and a total of not over about fifty carbon atoms. The compounds may have from one to four alkyl radicals per phenol nucleus.

The phenol contains at least one and preferably at least two phenolic hydroxyls, the two or more hydroxyls being in the same ring, if there is only one, or in the same or different rings, if there are more than one. In the case of bicyclic phenols, the rings can be linked by thio or oxy-ether groups, or by alkylene, alicyclidene or arylidene groups. Such phenols, which are preferred because of their superior stabilizing action, can be defined by the formula:

where X is an oxygen or sulfur atom, or an alkylene or alicyclidene or arylene or a mixed alkylene-alicyclidene or alkylene-arylidene group, having a straight or branched chain, whose total number of carbon atoms ranges from one to about eighteen, y and y are the number of phenolic hydroxyl groups OH, 12 and 21 are the number of R groups, and R and R are hydrogen or alkyl of one to about eighteen carbon atoms. Preferably, the OH groups are ortho and/0r para to X.

The sum of y and n in each ring cannot, of course, exceed five.

Typical X groups are The various X and R groups are exemplified in the following compounds.

Exemplary of satisfactory monohydric phenols are 2,6- di-tertiary-butyl-4-methyl phenol, 2-tertiary butyl 4- methoxy phenol, nonyl phenol, dodecyl phenol, dinonyl phenol, phenyl phenol, tetradecyl phenol, and tetrahydro-a-naphthol,

Exemplary polyhydric phenols are Orcinol,

Propyl gallate,

Catechol,

Resorcinol,

4-octyl resorcinol,

4-dodecyl resorcinol,

4-octadecyl catechol, 4-isooctyl-phloroglucinol, pyrogallol, Hexahydroxy benzene,

4-isohexyl-catechol,

2,6-ditertiarybutyl resorcinol,

2,6-diisopropyl phloroglucinol,

Methylenebis (2,6-ditertiarybutyl-m-cresol) Methylenebis (2,6-ditertiarybutyl-phenol) 2,2-bis (4-hydroxypl1enyl) propane, Methy1enebis(p-cresol),

4,4-thio-bis-phenol,

4,4'-oxobis 3-rnethyl-6-is opropyl-phenol) 4,4'-thiobis 3-methyl-6-tertiarybutyl-phenol) 2,2-oxobis (4-dodecyl-pheno1) 2,2-thiobis(4-methyl-6-tertiarybutyl-pheno1),

a 6 2,6-diisooctyl resorcinol, 4,4-n-buty1idenebis 2-tertiarybutyl-5 -methyl-pl1enol 4,4'-benzylidenebis 2-tertirybutyl-5-methyl phenol) 2,2-methylenebis (4-methy1-6-(1' methyl cyclohexyl)- phenol), 4,4-cyclohexylidenebis(2-tertiarybutyl-phenol), 2,6-bis(2'-hydroxy-3'-tertiary butyl 5'-methylbenxyl)- 4-methylphenol, 4-octyl pyrogallol, and 3,5-ditertiarybutyl catechol.

When the nickel glyoxime is used in conjunction with triphosphite, the enhanced efiect is evidenced in elimination of discoloration on aging imparted by the triphosphite in relatively high concentrations, thus permitting use of larger amounts of triphosphite.

The triphosphite can be any organic triphosphite having attached to phosphorus through oxygen or sulfur groups selected from aryl, alkyl, cycloalkyl, aralkyl and alkaryl groups, in any combinations, such as, three monovalent groups, (RA) P; one monovalent group and one bivalent group, forming a heterocyclic ring with the phosphorus,

a plurality of bivalent groups forming polymers therewith,

A A A1 P-AR1A-P Rl A \A one trivalent group,

A RA P and a plurality of trivalent groups forming polymers therewith,

and any combinations of monovalent, bivalent and trivalent groups to form monomeric and polymeric phosphites; wherein A is oxygen or sulfur. The term organic phosphite triester as used herein is inclusive of 0x0, thio and mixed oxo thio phosphites. Usually, the phosphite will not have more than about sixty carbon atoms.

Exemplary are Monophenyl di-Z-ethyl hexyl phosphite, Diphenyl mono-Z-ethyl hexyl phosphite, Diisooctyl monotolyl phosphite, Tri-2-ethyl hexyl phosphite, Phenyl dicyclohexyl phosphite, Phenylcliethyl phosphite, Triphenyl phosphite, Tricresyl phosphite, Tri(dimethylphenyl) phosphite, Trioctadecyl phosphite, Triisooctyl phosphite, Tridodecyl phosphite, Isooctyl diphenyl phosphite, DiisOoctyl phenyl phosphite, Tri(t-octylphenyl) phosphite,

tri(t-nonylphenyl phosphite, benzyl methyl isopropyl phosphite, butyl dicresyl phosphite, isoctyl di(octylphenyl) phosphite, di(2-ethylhexyl) (isooctylphenyl) phosphite, tri(2-cyclohexylphenyl) phosphite, tri-a-naphthyl phosphite, tri(phenylphenyl) phosphite, 'tri(2-phenyl ethyl) phosphite triclodecyl thiophosphite, tri-p-tert-butyl phenyl thiophosphite, didecyl thiodiphenyl phosphite, tertbutyl phenyl thio-di-2-ethylhexyl phosphite, ethylene phenyl phosphite, ethylene t-butyl phosphite, ethylene isohexyl phosphite, ethylene isooctyl phosphite, ethylene cyclohexyl phosphite, 2-phenoxy-1,3,2-dioxaphosphorinane, 2-butxy-1,3,2-dioxaphosphorinane, 2-oct0xy-5,5 dirnethyldioxaphosphorinane, and 2-cyc10hexyl0xy-5,S-diethyldioxaphosphorinane.

When the nickel glyoxime stabilizer is used in conjunction with a thiodipropionic acid ester, the improvement is evidenced by a materially prolonged resistance to embrittlernent and development of t-ackiness at elevated temperatures. The thiodipropionic acid ester has the following formula:

in Which R is an organic R radical selected from the group consisting of hydrocarbon radicals such .as alkyl, allcenyl, aryl, cycloalkyl, mixed 'alkyl owl, and mixed alkyl cycloalkyl radicals; and esters thereof with aliphatic carboxylic acids; and Y is selected from the group consisting of (a) hydrogen, (b) a second R radical R which can be the same as or different from the R radical, (c) a polymeric chain of n thiodipropionic acid ester units:

where Z is hydrogen, R or M; n is the number of thiodipropionic acid ester units in the chain; and X is a bivalent hydrocarbon group of the type of R that is, .alkylene, alkeny-lene, arylene, cycloalkylene, mixed alkyl arylene and mixed alkyl cycloal ky-lene radicals; the value of n can range upwards from 1, but there is no upper limit on n except as is governed by the ratio of carbon atoms to sulfur atoms as stated below; and (d) a polyvalent inetal M of Group II of the Periodic Table such as zinc, calcium, cadmium, barium, magnesium and strontium.

The molecular weights of the R and Y radicals are taken such that with the remainder of the molecule the thiodipropionic ester has a total of from about ten to about sixty carbon atoms per sulfur atom.

Accordingly, the various thiodipropionic acid ester species coming within the above-mentioned categories within the general formula can be defined as follows:

In the above formulae R and R M, X and Z are the same as before. In the polymer (c), as in the other forms of thiodipropionic acid esters, the total number of carbon atoms per sulfur is within the range from about ten to about sixty.

The R radical of these esters is important in furnishing compatibility with the polypropylene. The Y radical is desirably a different radical, R or M or a polymer, where R is rather low in molecular Weight, so as to compensate for this in obtaining the optimum compatibility and nonvolatility. Where Y is 'a metal, the thiodipropionic acid ester furnishes the beneficial properties of the polyvalent metal salt which is described below.

The aryl, alkyl, alkenyl and cycloalkyl groups may, if desired, contain inert, nonreactive substitutents such as halogen and other carbocyclic and heterocylic ring structures condensed therewith.

Typical R radicals are, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoarnyl, n octyl, isooctyl, 2-etlhyl hexyl, t-octyl, decyl, dodecyl, octadecyl, allyl, hexenyl, linoleyl, ricinoleyl, oleyl, phenyl, xy'lyl, tolyl, ethylphenyl, naphthyl, cyclohexyl, benzyl, cyclopentyl, rnethylcyclohexyl, ethylcyclohexyl, and naphthenyl, hydroxyet-hyl, hydroxypropyl, glyceryl, sorbityl, pentaerythrityl, and polyoxyalkylene radicals such as those derived from diethylene glycol, triethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, and polyoxypropyleneoxyet'hylene glycol, and esters thereof with any of the organic acids named below in the discussion of the polyvalent metal salts, including in addition those organic acids having from two to five carbon atoms, such as acetic, propionic, butyric and vale'ric acids.

Typical X radicals are alkylene radicals such as ethylene, tetramethylene, hexamethylene, decarnethylene, alkyland arylssubstituted alkylene radicals such as 1,2- propylene,

and

arylene radicals such as phenylene,

methylenephenylene,

dimethylene phenylene,

and alicycly'lene radicals such as cyclohexylene,

and cyclopentylene,

As exemplary of the thiodipropionic acid esters which can be used, there can be mentioned the following: monolauryl thiodipropionic acid, dilauryl thiodipropionate, butyl stearyl thiodipropionate, di-Z-ethylhexyl-thiodipropionate, diisodecyl-thiodipropionate, isodecyl phenyl thiodipropionate, benzyl lauryl thiodipropionate, benzyl phenyl thiodipropionate, the diester of mixed coconut fatty alcohols and thiodipropionic acid, the diester of mixed tallow fatty alcohols and thiodipropionic acid, the acid ester of mixed cottonseed oil fatty alcohols and thiodipropionic acid, the .acid ester of mixed soybean oil fatty alcohols and thiodipropionic acid, cyclohexyl nonyl thiodipropionate, monooleyl thiodipropionic acid, hydroxyethyl lauryl thiodipropionate, monoglyceryl thiodipropionic acid, glyceryl monostearate monothiodipropionate, sorbityl isodecyl thiodipropionate, the polyester of diethylene glycol and thiodipropionic acid,'the polyester of triethylene glycol and thiodipropionic acid, the polyester of hexamethylene glycol and thiodipropionic acid, the polyester of pentaerythritol and thiodipropionic acid, the polyester of octamethy-lene glycol and thiodipropionic acid, the polyester of p-dibenzyl alcohol and thiodipropionic acid, ethylbenzyl lauryl thiodipropionate, strontium stearyl thiodipropionate, magnesium oleyl thiodipropionate, calcium dodecylbenzyl. thiodipropionate, and mono(dodecylbenzyl) thiodipropionic acid.

These esters are for the most part known compounds, but where they are not available, they are readily prepared by esterification of thiodipropionic acid and the corresponding alcohol.

When the nickel glyoxime is used in conjunction with a polyvalent metal salt of an organic acid, the polyvalent metal salt of an organic acid will ordinarily have from about six to about twenty-four carbon atoms. The polyvalent metal can be any metal of Group II of the Periodic Table, such as zinc, calcium, cadmium, barium, magnesium and strontium. The alkali metal salts and heavy metal salts such as lead salts are unsatisfactory. The acid can be any organic non-nitrogenous monocarboxylic acid having from six to twenty-four carbon atoms. The aliphatic, aromatic alicyclic and oxygencontaining heterocyclic organic acids are operable as a class. By the term aliphatic acid is meant any open chain carboxylic acid, substituted, if desired, with nonreactive groups, such as halogen, sulfur and hydroxyl. By the term alicyclic it will be understood that there is intended any cyclic acid in which the ring is nonaromatic and composed solely of carbon atoms, and such acids may if desired have inert, nonreactive substituents such as halogen, hydroxyl, alkyl radicals, alkenyl radicals and other carbocyclic ring structures condensed therewith. The oxygen-containing heterocyclic compounds can be aromatic or nonaroinatic and can include oxygen and carbon in the ring structure, such as alkyl-substituted furoic acid. The aromatic acids likewise can have nonreactive ring substituents such as halogen, alkyl and alkenyl groups, and other saturated or aromatic rings condensed therewith.

As exemplary of the acids which can be used in the form of their metal salts there can be mentioned the following: hexoic acid, 2-ethylhexoic acid, n-octoic acid, isooctoic acid, capric acid, undecylic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, ricinoleic acid, behenic acid, chlorocaproic acid, hydroxy capric acid, benzoic acid, phenylacetic acid, butyl benzoic acid, ethyl benzoic acid, propyl benzoic acid, hexyl benzoic acid, salicylic acid, naphthoic acid, l-naphthalene acetic acid, orthobenzoyl benzoic acid, naphthenic acids derived from petroleum, abietic acid, dihydroabietic acid, hexahydrobenzoic acid, and methyl furoic acid.

The water-insoluble salts are preferred, because they are not leached out when the plastic is in contact with water. Where these salts are not known, they are made by the usual types of reaction, such as by mixing the acid, acid chloride or anhydride with the corresponding oxide or hydroxide of the metal in a liquid solvent, and heating, if necessary, until salt formation is complete.

The preferred stabilizer system of the invention comprises four or five stabilizers, the nickel glyoxime, a polyhydric phenol, a triphosphite, and a thiodipropionic acid ester, and optionally, a 2-hydroxy-benzophenone. An additional sixth ingredient which is included in the preferred systems of the invention, but which is not essential, is a polyvalent metal salt of an organic acid. These five and six stabilizers together give an enhanced stabilization which is not obtainable from any of them alone or in combinations of two or three. When taken alone, the components of this stabilizer system are capable only of inhibiting deterioration in one or two respects, and quite large amounts may be needed before any effect is noted. The components other than the nickel glyoxime in pairs may display a lesser stabilizing effect than any one alone. For example, the phenol alone gives an improved resistance to embrittlement and reduction in melt viscosity at elevated temperatures, but little assistance as to maintenance of color. The triphosphite alone is a rather poor stabilizer in preventing deterioration in the first two properties, but it does assist in resisting discoloration.

The thiodipropionic acid ester by itself only improves resistance to embrittlement. The polyvalent salt of an organic acid by itself prevents discoloration, but no more. In combination with the phenol, the color is worse than with the salt alone.

In combinations with the triphosphite, the usual discoloration is prevented, but black spots may be obtained upon aging at high triphosphite concentrations.

In view of this, it is surprising that the nickel glyoxime, phenol, triphosphite and thiodipropionic acid ester taken together in the same total amount not only prevent discoloration but also embrittlement and inhibit the increase in melt index, with accompanying degradation of physical properties, both upon exposure to light and at processing temperatures, and furthermore greatly enhance the resistance to discoloration and embrittlement on aging to far beyond that obtainable from the components individually. This enhanced stabilizing effect is obtained with any propylene polymer, regardless of the process by which it is prepared.

A very small amount of the nickel glyoxime is sufficient, with or without additional stabilizers, to improve the stability against deterioration in physical properties, including, for example, resistance to embrittlement, upon exposure to light under the conditions to which the olefin polymer will be subjected. Amounts within the range from about 0.001 to about 0.50% by weight of the polymer impart satisfactory resistance. Preferably, from 0.01 to 0.25% is employed for optimum stabilization.

If additional stabilizers are employed to obtain additional stabilization efiects, the amount of total stabilizer is within the range from about 0.005 to about 5%, preferably from 0.1 to 3%.

Preferably, the stabilizer system comprises from about 0.001 to about 0.25% of nickel glyoxime, from about 0.025 to about 0.5% of a phenol, and from about 0.05 to about 1% of a thiodipropionic acid ester, with, optionally, from about 0.025 to about 0.75% of a polyvalent metal salt, when present, and from about 0.01 to about 0.5% of a Z-hydroxy-benzophenone, when present.

If a combination of stabilizers is to be utilized, they may be formulated as a simple mixture for incorporation in the polymer by the polymer manufacturer or by the converter. An inert organic solvent can be used to facilitate handling, it the ingredients do not form a homogeneous mixture or solution.

The stabilizer of the invention is also applicable to olefin polymers prepared by any of the various procedures, using the available catalysts, such as the Ziegler, ICI, Union Carbide, Du Pont, Phillips, Montecatini, Esso and Standard Oil (Indiana) process polymers (Chem. & Eng. News, November 21, 1960, pp. 3659), for the molecular weight and tacticity are not factors affecting this stabilizer.

Formerly, olefin polymers prepared by these processes contained traces of catalyst residues. These residues materially diminished the stability of the olefin polymer, despite efforts to overcome the problems by addition of polyvinyl chloride resin stabilizers, whose function was to act on the halogen or halide of the catalyst in the same manner as on the halogen or liberated halide of the polyvinyl chloride resin. It is now customary to remove catalyst residues substantially completely, so that the addition of polyvinyl chloride resin stabilizers is no longer indicated. The stabilizers of the invention are effective with olefin polymers substantially free from catalyst residues, although they can also be used with catalyst-containing polymers with good results.

Isotactic polypropylene, available commercially under the trade names Pro-Fax, Escon and Olefane and having a softening or hot-working temperature of about 350 F. is an example of a sterically regular polypropylene polymer.

Propypropylene solid polymer can be defined in a manner to differentiate it from other polyolefins as having a density within the range of from 0.86 to 0.91, and a melting point above C. The stabilizer of the invention is applicable to all such polypropylenes, as distinguished from polypropylenes in the liquid form or in semiliquid or gel-like forms, such as are used as greases and waxes.

Mixtures of olefin polymers such as propylene polymers with other compatible polymers and copolymers of propylene with copolymerizable monomers such as ethylene and butene also can be stabilized in accordance with this invention. For example mixtures of polyethylene and polypropylene, and copolymers of propylene and 6501) together with 0.25 part of dilauryl thiodipropionate, 0.06 part of zinc 2-ethyl hexoate and 0.19 part of the product of the transesterification of one mole of triphenyl phosphite, 0.5 mole of 4,4'-n-butylidene-bis-(2- tert-butyl-S-methyl-phenol), 2 moles of tridecyl alcohol, and 0.9 g. of sodium hydroxide at 110 to 170 C. for 3 hours. This polymer as supplied had a melt index of 3.0, ASTM Dl23857T at 230 C. The mixture so prepared was in each case placed on a 2-roll mill and fluxed for five minutes at l70i2 C. mil slabs were then molded from each test composition, and exposed to sunlight in Arizona for nine months together with the unstabilized polymer.

Table l Unexposed 3 months 4 months 7 months 9months ExlaImple N iokel Stabilizer Amount Melt Oondi- Melt Condi- Melt Condi- Melt Condi- Melt Condi- Index tion Index tion Index tion Index tion Index tion None 0 3.0 Good 100 Brittle N1 keldnnethyl 0.2 3.0 o 3.1 Good.. 3.1 Good 3.3 Good--." 100 Very glyoxime. brittle. Nlekeloetylphenol- 0.5 2.9 ...do 8.7 Brittle 100 Very Disentegrated. Nlllfildg. thl 1 08 brittle.

gai 5,3 3 fi fi g 3.0 -do...- 3.2 Good--. 3.4 Good 6.1 Slightly 4-n-octyl-oxybenz0- brittle phenone.

B ggggg ggg ggpg- 2.2 -do 2.5 do 27 Britt1e 100 very 4-n-ootyl-oxybenzobnttle' phenone.

3 ggggg gggi 3:} 3.0 ...do 3.1 do 3.3 Good 9.6 Slightly hydroxy-t-n-octylbrittle. oxybenzophenone.

O figl g gl g 3.1 do 3.7 Slightly- 4o Brittle Disintegrated.

hydroxyA-n-oetyloxybenzophenone.

polystyrene. The term olefin polymer encompasses The above data clearly indicate that the nickel glyoxime both homopolymers and copolymers, as well as mixtures of olefin polymers.

The stabilizer is incorporated in the polymer in suitable mixing equipment, such as a mill or a Banbury mixer. If the propylene polymer has a melt viscosity which is too high for the desired use, the propylene polymer can be worked until its melt viscosity has been reduced to the desired range before addition of the stabilizer. However, propylene polymers in a range of workable melt viscosities are now available. Mixing is continued until the mixture is substantially uniform. The resulting composition is then removed from the mixing equipment and brought to the size and shape desired, for marketing or use.

The stabilized olefin polymer can be worked into the desired shape, such as by milling, calendering, extrusion or injection molding or fiber-forming.

The stabilizing effect of the nickel glyoximes of the invention was evaluated in the working examples which follow using a modified ASTM D1238-57T test procedure for determining melt index, using a 2160 g. weight load on the plastometer piston, comparing melt index before and after exposure of the polymer to sunlight at the Desert Sunshine Exposure Test Station at Phoenix, Arizona, for a test period of nine months. This ensured stability to less severe sunshine conditions for considerably extended periods. The change in melt index for this period is an accurate measure of the degree of light stabilization imparted by the stabilizer added, irrespective of the numerical value of the initial melt indices of the different samples of one particular polymer. The lower ratio, the less the change, and the greater the stabilizing eflfect.

EXAMPLES 1 TO 3 In accordance with this invention the nickel glyoxime and benzophenone listed in the table which follows were weighed and dispersed by hand stirring in 100 parts of powdered previously unstabilized polypropylene (Profax and benzophenone increased the resistance of the polymer to degradative deterioration on prolonged exposure to sunlight. Example 1 shows that the melt index after seven to nine months exposure was far lower for the polymer containing the nickel glyoxime than after three months exposure for the control polymer not stabilized in accordance with this invention, and superior to the Control A, the polymer stabilized by the nickel octylphenol sulfide of the prior art.

Examples 2 and 3 show the enhanced eflect of the benzophenone when combined with the nickel glyoxime. Examples 2 and 3 are superior to Example 1 at the end of nine months exposure, even though the amount of nickel is only 40 to 80% of the amount of Example 1. Examples 2 and 3 are far superior to Controls B and C, showing that the synergism with the compounds of the invention is quite marked, but almost insignificant, especially after nine months exposure, for the nickel octylphenol-sulfide.

EXAMPLE 4 Polypropylene was stabilized against light deterioration by the addition of nickel diphenyl glyoxime. 0.25 part of stabilizer was weighed and dispersed by hand stirring in 100 parts of powdered previously unstabilized polypropylene (Pro-fax 6501). This polymer as supplied had a melt index of 3.0 ASTM D1238-57T at 230 C. The mixture was in each case placed on a 2-roll mill and fluxed for five minutes at l70- t2 C. Pieces and control strips cut from a milled sheet made from the sample composition were exposed in the Weatherometer at 52 C. black panel temperature and examined at intervals for ability to withstand cracking when bent. Failure was de termined as the time when the piece cracked when bent.

13 The data of Table II clearly indicates that the addition of a light stabilizer of this invention markedly improved the resistance of the polymer to degradation due to exposure to light.

EXAMPLE The polypropylene of Example 4 was stabilized by addition of nickel glyoxime and 4,4-thiobis(2-t-butyl-5- methyl phenol) as an additional stabilizer in accordance with this invention. A total of 0.15% glyoxime and 0.1% phenol was used. This composition was compared with a polypropylene containing only 0.1% of the phenol as a control.

The stabilizers were weighed and dispersed by hand stirring in the polypropylene. The mixture was placed on a 2-roll mill and fluxed for five minutes at 170:2 C. Strips of each sample composition were exposed in the Weatherometer at 52 C. black panel temperature and examined at intervals for ability to withstand cracking by bending.

- Table III Example No.: Hours to failure Control 100 Example 5 266 /3 The data of Table III clearly indicate that the addition of a nickel glyoxime stabilizer of this invention as additional stabilizer to a polypropylene resin stabilized with a conventional phenol heat stabilizer markedly improves the resistance of the polymer to degradation due to exposure to light.

EXAMPLES 6 AND 7 Low density DYNH and high density Hi-fax polyethylene was stabilized by the addition of 0.1% nickel dimethyl glyoxime. The stabilizer was weighed and dispersed by hand stirring in 100 parts of the polyethylene. The DYNH polymer as supplied had a melt index of 2.3 ASTM D1238-57T at 193 C. The Hi-fax polymer had a melt index of 1.1 ASTM D1238-57T at 193 C. The mixture was in each case placed on a 2-roll mill and fiuxed for five minutes at 170i2 C. Pieces cut from the milled sheet were placed in a 6" x 6" x 0.04" mold and molded at 350 F., at a pressure of 1,000 p.s.i., for 5 minutes. The molded specimen was then cooled to 100 F., the pressure released and the slab so formed was removed.

In testing the polyethylene plastic so molded, the specimen is exposed to ultraviolet light and air in a Weatherometer, in this case Model XW operating at a black panel temperature of 125 F. Sections of the plastic undergoing test are removed at intervals and tested for the lowest temperature at which the slabs, upon severe cooling, do not show brittleness on bending. This brittleness temperature is determined essentially according to ASTM Specification D746-52T. It is the lowest temperature at which half of the exposed specimens do not crack when the tests are made at 10 intervals. When the brittleness temperature was F., for example, half, at least, of the samples did not crack at 14 The data of Table IV clearly indicate that the addition of nickel dimethyl glyoxime to a polyethylene resin markedly improves the resistance of the polymer to degradation due to exposure to light.

EXAMPLES 8 TO 10 In accordance with this invention nickel stearate and dimethyl glyoxime in the amounts given in the table which follows were weighed and dispersed by hand stirring in parts of powdered previously unstabilized polypropylene (Pro-fax 6501) together with 0.25 part of dilauryl thiodipropionate, 0.06 part of zinc 2-ethyl hexoate and 0.19 part of the product of the transesterification of one mole of triphenyl phosphite, 0.5 mole of 4,4'-n-butylidenebis-(Z-tert-butyl-S-methyl phenol), 2 moles of tridecyl alcohol and 0.9 g. of sodium hydroxide at to C. for 3 hours. This polymer as supplied had a melt index of 3.0, ASTM Dl238-57T at 230 C. The mixture so prepared was in each case placed on a 2-roll mill and fiuxed for five minutes at 170i2 C. Pieces cut from the milled sheet were exposed in the Weatherometer at 52 C. black panel temperature and examined at intervals for ability to withstand cracking by bending.

1 N 0 failure by end of test.

The data of Table V clearly indicate that the addition of a light stabilizer of this invention as additional stabilizer to a polypropylene resin stabilized with heat stabilizers markedly improves the resistance of the polymer to degradation due to exposure to light.

We claim:

1. A stabilizer combination for use in improving the resistance of olefin polymers to deterioration in physical properties on exposure to light, consisting essentially of from about 0.1 to about 50 parts by weight of a nickel glyoxime and from about 0.4 to about 500 parts by weight of another olefin polymer stabilizer, said stabilizer being compatible with polypropylene and having a. low vapor pressure at polypropylene working temperatures.

2. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a phenol.

3. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a bicyclic phenol.

4. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a triphosphite.

5. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a metal salt of an organic non-nitrogenous monocarboxylic acid having from six to twenty-four carbon atoms and a polyvalent metal of Group II of the Periodic Table.

6. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a thiodipropionate.

7. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime and a 2-hydroxy-benzophenone.

8. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime, a phenol, a triphosphite, and a thiodipropionate.

9. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime, a phenol, a triphosphite, a thiodipropionate, and a metal salt of an organic non-nitrogenous monocarboxylic acid having from six to twenty-four carbon atoms and a polyvalent metal of Group II of the Periodic Table.

10. A stabilizer combination in accordance with claim 1 consisting essentially of a nickel glyoxime, a phenol, a triphosphite, a thiodipropionate, a metal salt of an organic non-nitrogenous monocarboxylic acid having from six to twenty-four carbon atoms and a polyvalent metal of Group II of the Periodic Table, and a Z-hydroxy-benzophenone.

11. An olefin polymer composition having improved resistance to deterioration upon exposure to light comprising an olefin polymer and from about 0.001 to about 0.5 by weight of the polymer of a nickel glyoxirne.

12. An olefin polymer composition in accordance with claim 11 in which the olefin polymer is a propylene polymer.

13. An olefin polymer composition in accordance with claim 12 in which the propylene polymer is polypropylene.

14. A propylene polymer composition having improved resistance to deterioration upon exposure to light comprising a propylene polymer, from about 0.001 to about 0.5% by weight of the polymer of a nickel glyoxime and from about 0.004 to about 5% by weight of the polymer of another propylene polymer stabilizer, said stabilizers being compatible With the polymer and having a 10W vapor pressure at propylene polymer working temperatures.

References Cited by the Examiner UNITED STATES PATENTS 5 2,465,296 3/1949 Swiss 26045.75 2,615,860 10/1952 Burgess 260-45.75 2,860,115 11/1958 Hecker et al 26023 2,861,053 11/1958 Lappin et a1. 26045.95 10 3,069,369 12/1962 Galbraith et al 260-23 FOREIGN PATENTS 577,252 7/1959 Belgium. 608,408 1/ 1962 Belgium. 638,674 3/1962 Canada. 15 889,680 2/1962 Great Britain.

OTHER REFERENCES 'Noller: Chemistry of Organic Compounds (1957), 20 page 770.

LEON I. BERCOVITZ, Primary Examiner. R. A. WHITE, Assistant Examiner. 

11. AN OLEFIN POLYMER COMPOSITION HAVING IMPROVED RESISTANCE TO DETERIORATION UPON EXPOSURE TO LIGHT COMPRISING AN OLEFIN POLYMER AND FROM ABOUT 0.001 TO ABOUT 0.5% BY WEIGHT OF THE POLYMER OF A NICKEL GLYOXIME. 